1. Field of the Invention
The invention relates in general terms to the plasma coating of containers, and in particular the invention relates to the spectroscopic monitoring of the coating process.
2. Description of Related Art
It is known to provide containers, such as in particular bottles, with barrier layers. These barrier layers are produced, inter alia, by chemical or physical vapor deposition. These processes can produce relatively thin layers with a high barrier action.
In particular plasma-enhanced or plasma-induced vapor deposition has proven a suitable chemical vapor deposition process; in this process, a plasma is ignited in a process gas by means of electromagnetic energy, and the reaction products which form in the plasma are deposited as a layer on the container.
This process is, inter alia, particularly suitable for the inexpensive coating of large quantities of workpieces, for example for coating plastic bottles in order to improve the barrier properties.
In this context, there is a demand for it to be possible to monitor the process sequence in a simple way and to detect incorrect coatings or workpieces quickly.